Winter pruning

Sunday, 03 June 2018

Ulmus parvifolia, the Chinese elm, on a bleak winter day

It's often hard to psyche oneself up to get out into the garden on cold, bleak days like Saturday was. However, once one actually gets outside, there are lots of tasks to do and one soon warms up with all the exertion. At the end of the gardening stint, there can a quiet glow of satisfaction at what has been achieved!

Apart from moving plants around that are in the wrong place, sweeping and composting autumn leaves, encouraging growth in vegetables and spring bulbs with liquid fertiliser, and dividing some perennials, the main winter task in my garden is pruning. I spread the job over June, July and August (with just a little bit more in September), partly so that my garden isn't too bare through the whole of winter, partly to make it less onerous work, and partly because different plants seem to respond best to pruning in different months.

Daphne odora f. alba: do not prune until after flowering!

It is important NOT to prune certain plants in winter, such as winter- or spring-blooming shrubs like Deutzia or Daphne, as you will be simply cutting off all the flowering wood! They are best cut back straight after their flowers have faded later in the year.

Ageing head of Kniphofia ensifolia with Canna Striata: the Canna foliage needs to be cut to the ground now

In June, I focus on tidying up the remains of plants that are dying down at this time, or looking quite hideous. The foliage of Canna plants looks appalling at this time, disfigured and often with patches of rust. I cut all the leaves off at ground level and put them in the green bin, not the compost heap, in an effort not to spread the rust around the garden. I also check at this time to see if the Canna clumps are getting too congested or spreading beyond their allocated area; if they are, I dig them up, potting some up for give-aways to friends.

Also often afflicted by rust at this time of year are my clumps of daylilies, and this is an ideal time to cut all the foliage of these right to the ground. Again, this goes into the green bin. Fresh new growth will appear before too long. If these clumps are overcrowded, they can also be divided up at the same time. I also cut my Kniphofia leaves to the ground when they have finished flowering. I give these to a creative friend who dries them then weaves them into amazing baskets!

Miscanthus sinensis Sarabande; these have now been cut to the ground

The dying leaves of my big specimens of ornamental grasses (Miscanthus cultivars and Pennisetum setaceum) are also cut to the ground in June. We use a hedge trimmer for this job as the plants are quite wide, and this makes the task a breeze. It's important to do the cutting now, as new foliage will start to grow sooner than we imagine it will, and if the old growth isn't removed before that time, the new leaves will be chopped off as well when it is finally cut back.

Dahlia Mt Noddy: the dead stalks of Dahlia should be cut to the ground now

I don't grow many herbaceous perennials but I do have a few: sentimental favourites from my cottage garden years. These are all cut back to their basal rosettes (or to the ground if completely deciduous) now - Japanese windflowers, Echinacea purpurea, Teucrium hyrcanicum , Nepeta cultivars, perennial phlox and Solomon's seal. The Dahlia plants, showy divas of the summer borders, are dying back quite horribly now as the cold weather finally sets in, and these will be cut to the ground this month. This leaves quite a large bare area, but I usually put a layer of compost over the top of the dormant tubers and sow seeds of a crop of fast-growing winter crops such as rocket, mizuna or lamb's lettuce (or a herb such as coriander or chervil) directly onto the space, which will cover the empty ground nicely and give me pickings for a salad bowl all through winter!

A white version of Plectranthus ecklonii: to be pruned lightly now

As I grow many warm-climate shrubby perennials, these will not be pruned until August, as I feel that heavy pruning in the coldest months can make them vulnerable. (Those who live in warmer coastal areas probably need have no such qualms!) However, I do lightly trim over plants such as Plectranthus and Ruellia now to remove deadheads and neaten them up. I tackle most of my shrubby Salvia plants in August too (except those still in full bloom at that time!), but those types that throw up new shoots at their base now - such as 'Meigan's Magic', the Salvia leucantha species and cultivars, and 'Phyllis' Fancy' - will have their old woody branches cut out at the base when they finish flowering in June or July (by which time I can't stand their straggly form any longer!).

Traditionally, July sees the pruning of Hydrangea (though it can also be done in February, which I tend to do these days), Buddleja, roses and Fuchsia hybrids. Deciduous and evergreen trees can also be shaped if necessary at this time, as can sasanqua Camellia if they need to be clipped (for example, if used as a hedge) or neatened. Old wood can be removed from citrus trees in July.

I prune my Begonia plants in mid-August

Mid-August is when I do all my warm-climate shrubby perennials (for example, the rest of my Salvia, all my Plectranthus, all my Acanthaceae plants and Begonia), and cold-sensitive foliage plants such as Iresine and Alternanthera, along with evergreen shrubs, including japonica Camellia - and it is indeed a busy time!

Reader Comments

  • By margaret 2122 (Zone:10 - Warm Temperate) Monday, 04 June 2018

    Thank you for presenting the time frame for cutting back plants. I have not ever cut my canna or daylily to the ground, but this is a good idea, as they do tend to suffer from rust. This year, I have given my plectranthus a light prune and will do a harder one later. Dahlia, Michaelmas daisy, windflower and chrysanthemum have all finished flowering and these are being cut back, and moved, where applicable. Begonia, especially canes, are better cut back at the end of August. Thanks for the information on the begonias, Margaret! Deirdre

  • By Kerrie 2104 (Zone:10 - Warm Temperate) Monday, 04 June 2018

    This is a great post Dierdre as pruning confuses me & i seem to fail at it. My Lion"s tail plant was way out of control so i cut it back about a month ago after flowering & a huge chunk of it has died. Same thing happened to my Blue Witches Hat plant which completely died. I was lucky enough to replace it as it"s a bit rare. My salvia Santa Barbara took forever to come back after pruning but was gorgeous this year finally. Have you considered doing one of your books on pruning, when & how? I do think that some plants get old and woody and do not respond well at that point to pruning -- better to replace them. I might make a page on the website about pruning at some stage! I have tried to mention pruning information for plants on the Plant Reference. Deirdre

  • By Mandy 2515 (Zone:10 - Warm Temperate) Saturday, 09 June 2018

    Re. the Acanthaceae Family. I noted your information about Pachystachys lutea (yellow form). You noted that you hadn"t seen the red form in a Sydney garden. I believe I have one growing happily in Austinmer NSW. Not sure how to upload a photo if you need it. I"m taking my first cuttings this austumn. Mandy. Thanks, Mandy. It is great to know it grows in Sydney. I was recently able to purchase one online and am hoping it will grow as well as the yellow species. Deirdre

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